Micromechanical sensors are generally made up of a sensor element and an evaluation circuit which converts the quantities measured by the sensor element into utilizable signals. For this purpose, the sensor element and the evaluation circuit are typically housed in different structural elements. The electrical connection between the sensor element and the evaluation circuit is then achieved via bonding pads on both structural elements. If the sensor element and the evaluation circuit are positioned next to each other on one structural element, then this electrical connection can be achieved through circuit traces that are integrated in the structural element or applied on the structural element.
If the sensor element and the evaluation circuit, however, are positioned next to each other on the same upper side of the substrate, then, given an increasing desire for miniturization, it is necessary to take the associated necessary surface requirement into account. Thus, for example, additive integrations have been proposed for some time, in which a sensor structure is applied on a ready-processed electronic chip with the aid of a low-temperature process, for example metals using electroplating or silicon-germanium using a low-pressure deposition method.
Furthermore, given an increasing demand on the resolution capability of the sensors and hence on the signal-noise ratio of the combined system of sensor segment/evaluation electronics, it becomes necessary to reduce the parasitic elements produced to a significant extent by the leads. One design approach to this problem provides for a monolithic integration of the sensor segment and the evaluation electronics. An alternative design approach provides for an additive integration of the sensor segment and the evaluation electronics. Here, under the state of the art, the sensor segment is mounted subsequently onto a finished evaluation circuit.
German Patent Application No. DE 101 23 039 describes a sensor set-up in which a connection between sensors and evaluation electronics is established at least partly in the cover segment that is necessary in any event.
A further possibility for integrating the sensor elements and the readout circuit in one structural element is described in German Patent Application Nos. DE 100 42 945 and in DE 100 58 864. In the structural element thereby proposed, a sensor element is positioned vertically in relation to the readout electronics. In German Patent Application No. DE 100 42 945, the sensor element and the readout electronics are separated from each other by a hollow space with supporting structures, the supporting structures constituting at the same time an electrical connection between the sensor element and the readout circuit.
German Patent Application No. DE 100 58 864, by contrast, describes a micromechanical structure for integrated sensor set-ups, in which different layer sequences are applied on a substrate and processed. Selective etching of the applied layers produces metal structures that support the micromechanical structure and provide the electrical contacting of the readout electronics lying vertically below the sensor structure.